Apex, this voltage is only test... Now I'm on my work (informatica) when I get home, I check this problem in HV350.

Thank you !

Ok, I use fets from many factorys IR, Fairchild, Haris... and gate voltage for bias is very diferent 2,5-3,5V (5-7V gate to gate), but that can be easy set by change 470R in base to colector of 2N5551 (BC546).
Regards